The increasing development of optical fibers for communications purposes has created a need for a quick and inexpensive means of precisely aligning and coupling an optical fiber to a light emitter or detector. While a variety of such emitters or detectors are employed, the method of aligning and coupling is similar.
Semiconductor lasers, because of their compact size and high light output, are particularly well suited for use as emitters. The higher light output attainable extends the transmission range and reduces the number of optical amplifiers in the transmission path. The peak light-emitting area of the semiconductor laser, however, is not uniform. This area, while within the laser-emitting stripe, significantly varies among devices. Therefore, individual alignment of each laser and fiber is required to achieve low optical coupling loss. For similar reasons, individual alignment is also required for light-emitting diodes and photodiodes.
It is known (Bell System Technical Journal, March 1972, pages 573-594) to mount both the laser and fiber on separate holders and use micromanipulators to move the holders and thereby attain the desired alignment of laser and fiber. The optimum positioning is then secured by epoxy. The technique is time consuming and requires the use of precision fixturing.
The use of V-grooves on the orthogonal faces of a coupler block is disclosed by G. D. Khoe et al in U.S. Pat. No. 4,030,811, issued on June 21, 1977. This procedure requires precise initial placement of the laser on a cylindrical mounting rod. The laser position is then adjusted by sliding the rod in a V-groove disposed in a coupler block. Fabrication of the block is expensive and the laser mounting arrangement provides marginal thermal dissipation capacity due to the limited contact area between mounting rod and V-groove. This exiguous dissipation capacity substantially increases the likelihood of premature laser failure.
In U.S. Pat. No. 4,065,203 to Goell et al, issued Dec. 27, 1977, the use of a stepped header or mounting apparatus for a laser and optical fiber is disclosed. Both of these elements are located on different levels and with the aid of epoxy are aligned. As epoxy deteriorates under varying temperature and humidity conditions, this technique does not possess long term stability required in telecommunications applications.